A few years ago, large-scale denial-of-service attacks against game servers were making the news and becoming a frustratingly frequent occurrence in online gaming and e-sports. To protect its own games, Valve has for a number of years been working on developing a networking infrastructure that makes the system more resilient against denial-of-service attacks and lower latency to boot, and the company is using this system for both Dota 2 and CS:GO.

At 30 different locations around the world, Valve has established relaying servers that route networking traffic between clients and servers. These relay points provide DoS-resilience in several ways. They’re equipped with an aggregate of several terabits of bandwidth, so they can handle a certain amount of flooding in any case. Games can also switch from one relay to another without necessarily interrupting their connection. This switching can be to another relay in the same location or even to another point-of-presence entirely.